The county was named for John Montgomery, a soldier in the American Revolutionary War and an early settler who founded the city of Clarksville.

(In 1790, North Carolina had ceded its western lands to the Federal government to create what was also known as the Southwest Territory.)

Later acts of the Tennessee General Assembly had further reduced Montgomery County by 1871 to its current size and boundaries.

Cooper Creek Cave shows evidence of extensive mining and contains the remains of "many saltpeter hoppers."

Dunbar Cave is reported to have been mined for saltpeter during the Mexican War of 1848, but commercial development has destroyed any evidence of this.

Little mining is likely to have happened here during the Civil War, since the Union Army captured and occupied this part of Tennessee in early 1862.

Dunbar Cave was extensively used by prehistoric Indians, who inhabited this area for thousands of years before European encounters.

Remains of their cane torches have been found in the cave, and archaeologists have excavated numerous artifacts inside the entrance.

Subsequent investigations by archaeologists from the University of Tennessee at Knoxville confirmed the drawings were from people of the Mississippian culture, which was active about 1000-1300 CE.

In 2010, the State of Tennessee closed Dunbar Cave to the public because White Nose Syndrome was diagnosed in a bat, and they did not want the disease to spread.

Although Montgomery County is a Republican stronghold, the city of Clarksville has been competitive for both major political parties.

Portions in Fort Campbell however are zoned to Department of Defense Education Activity (DoDEA) schools.